Vimes, definitely. But the only Carrot novels I've read have been G!G! and FoC. I just finished FoC and there was a bit at the end:

'There was a glint in [Carrot's] eye that Igneous should have noticed.'

This is when the troll is refusing to give Dorfle a tongue. It struck me as the only time I remember there being any hint that Carrot could have the potential to be really nasty. At the very least, it hinted that he has some teeth, somewhere down under his charm and rather dull charisma. I thought this was particularly interesting.